Shell of differential speed variator for automobile

The invention relates to a shell of a differential speed variator for an automobile. The shell of the differential speed variator for the automobile comprises a box cover and a box body. The box cover and the box body are fastened together and are locked through a bolt and nut component. A power input hole and power output hole are formed in the box cover. An annular boss and an annular rib are arranged with the power input hole as the center of a circle, and the diameter of the annular boss is smaller than that of the annular rib. Strip-shaped ribs which are distributed in a divergent shape are further arranged with the power output hole serving as the center of a circle. The inner side end of each strip-shaped rib is connected to the first annular boss. The outer side ends of part of strip-shaped ribs stretch out of the annular rib, and the outer side ends of the rest strip-shaped ribs are connected with a positioning column arranged on the annular rib. The number of the strip-shaped ribs at one side close to the power input hole is larger than that of the strip-shaped ribs at one side far away from the power input hole. The parts, located between the annular rib and the annular boss, of the strip-shaped ribs are coplanar with the annular rib and the annular boss. The depths of the parts, located outside the annular rib, of the strip-shaped ribs are decreased gradually until the parts are flushed with the box cover. The intensity of the power input hole and the power outlet hole of the box cover are increased, and the box cover can bear a comparatively large torque when the differential speed variator for the automobile works.